Habits are formed by the repetition of particular acts. They are strengthened by an increase in the number of repeated acts. Habits are also weakened or broken, and contrary habits are formed by the repetition of contrary acts. – Mortimer J. Adler

To fall into a habit is to begin to cease to be. – Miguel de Unamuno, The Tragic Sense of Life

Habit is thus the enormous flywheel of society, its most precious conservative agent. It alone is what keeps us all within the bounds of ordinance, and saves the children of fortune from the envious uprisings of the poor. – William James, The Principles of Psychology